well...you could mark them? This is an open-sourced project - it's only as good as we make it.
Why would you want to mark them? Wouldn't that attract more people to your favorite or good producing lakes and put more pressure on them? Hence you would have to go farther to catch quality fish.
Ask anyone in the States what kind of fish they used to have in there lakes until people started talking, especially on the internet. I think when you help someone out you think a little bit about the person, is he or she ethical? or if they are going to tell alot of people etc. Kinda like would you tell your bait store operator your secret lake?
When you put info on the internet it is there forever and you don't know if they are ethical or not.
Just my two cents!